Satellite-based run-offmodel for monitoring drought in Peninsular Malaysia

Abstract

Traditional in situ observation interpolation techniques that provide rainfall data from rain gauges have limitations because they are discrete point-based data records, which may not be sufficient to assess droughts from a spatiotemporal perspective. Considering this limitation, this study has developed a run-offmodel-a fully satellite-based method for monitoring drought in Peninsular Malaysia. The formulation of the run-offdeficit uses a water balance equation based on satellite-based rainfall and evapotranspiration data extracted respectively from calibrated TRMM multi-satellites precipitation analysis data (TMPA) and moderate resolution imaging spectroradiometer data (MODIS). The run-offdeficit was calculated based on per pixel spatial scale and allowed to produce the continuous and regular run-offmaps. The run-offmodel was tested and evaluated in a one drought year (2005) within a span of three years (2003-2005) over the Kelantan (3448 km2) and Hulu Perak (3672 km2) catchments of Peninsular Malaysia. The validation results show that (1) monthly TMPA rainfall and MODIS evapotranspiration data significantly improved after calibration; (2) satellite-based run-offdata is not only strongly correlated with actual steam flow, but also with spatiotemporal variation of run-offin drought-affected forest catchments. The most severely drought-affected forest catchments that experienced the run-offdeficits were Hulu Perak, Ulu Gading, Gunung Stong and Relai over Kelantan. The real time run-offchange analysis shows that drought started in January and reached its peak in July of 2005. It was therefore demonstrated that this fully satellite-based run-offdeficit model is as good as a conventional drought-monitoring indicator, and can provide not only drought distribution information, but it also can reflect the drought-induced impacts on stream flow, forest catchment and land-use.